One boiler temp for CH and DHW

CBRob

I've got the old munchkin to back up and running. It does not have the vision one set up so it gets one high temperature limit setting and that's it.
I only need 120 for the heat and it has a very large indirect tank for domestic hot water, not sure of the gallons but it's 6 ft tall. What temperature would you choose for a high end one size fits all. The boiler was set with the factory limit of 180, I tried turning it down to 170 just to see how things work. What would you set it at?
I think it has a factory Delta temp of 30
Does that mean if I said a high in limit of 160 it would always be condensating and efficient? Is 160 hot enough to heat up domestic hot water and reasonable amount of time?
Within injection pump going to the radiant heat loop do I need higher temps then I am thinking?

CBRob

Here is the indirect tank.
And the little hx for the snow melt.
The mixing valve seems unnecessary.
Doubt the little hx is going to heat shock the slab

mattmia2

You probably won't be doing much condensing at 160. The radiant loop shouldn't need much more than 120 from the boiler. the temp you will need for dhw will depend o the delta t with the incoming and outgoing water, your usage profile, the size of the tank, and the size of the hx in the tank.

CBRob

I think the boiler has a differential that I can set, 5 to 30 degrees.
I didn't check yo see what it was set at.
Not much else to adjust with this older boiler.
I think from 2002.

CBRob

I figured out how to change the set point and differential temps.

I set high set point at. 165, down from 180.
Set the differential to 25 degrees.
Boiler shuts off the flame at about 167 and cools to 140 before firing again.

The boiler does not use the integrated primary circ pump wiring, it has a pump running 24/7 .

I might look into changing this.
I wonder if the circ pump will keep running in between differential temps when the flame is off?

EBEBRATT-Ed

Since you only need 120 for heat, set the boiler temp as low as possible to satisfy the dhw.
I would try 140-150 as the lowest temp